The invention relates to a cleaning solution for substrates of electronic materials, and particularly to a cleaning solution for removing metallic impurities and particle contamination adsorbed by substrates having metallic wiring in semiconductor manufacturing.
A trend for higher integration of ICs has brought about the need for strict contamination control, because trace impurities have a considerable effect on the properties and yield of devices. Which means that the concentration of metallic impurities and the presence of particles on the substrate need to be strictly controlled; for this purpose different types of cleaning solutions are used in the different processes of semiconductor manufacturing.
In general, mixed solutions of sulfuric acid-aqueous hydrogen peroxide, ammonium water-aqueous hydrogen peroxide-water (SC-1), hydrochloric acid-aqueous hydrogen peroxide-water (SC-2), diluted hydrofluoric acid, etc. are used as cleaning solutions for cleaning substrates of electronic materials such as semiconductor substrates, and depending on the purpose, each cleaning solution can be used on its own or in combination with other cleaning solutions.
Further, in recent years chemical mechanical polishing (CMP) technology has been introduced into semiconductor manufacturing processes for the planarization of insulation films, the planarization of contact holes, for damascene wiring, etc. CMP is a technology for polishing and planarizing insulation films and metallic materials by simultaneously using the chemical and physical effects, when a wafer is pressed against a polishing cloth called buff and is rotated while feeding a slurry, a mixture of abrasive particles and chemicals.
The slurry used in metal CMP (W and Cu-CMP) is a combination of abrasive particles (alumina, silica, manganese dioxide, cerium oxide, zirconium oxide, etc.) and an oxidizer (iron(III) nitrate, aqueous hydrogen peroxide, etc.). Therefore, after the CMP process, the substrate surface is contaminated by metallic impurities and abrasive particles from the slurry, as well as by polishing waste. Especially when iron(III) nitrate is used as oxidizer, there is the fear that due to the contamination by a high Fe concentration, a secondary contamination, polluting the production line, occurs in addition to the deterioration of the electrical properties of the substrate itself.
Consequently, the metallic impurities and the particles adhering during the CMP process need to be speedily removed before passing to the next process.
In the CMP treatment of interlayer insulation films, dilute hydrofluoric acid is used for removing metallic impurities and ammonia water is used for removing particles.
However, since dilute hydrofluoric acid corrodes metallic materials it cannot be used for cleaning after Cu and W-CMP.
An aqueous solution of citric acid is reported in Semiconductor World, p. 92, No. 3, 1997 as a cleaning solution not corroding metallic materials. Moreover, JP, A, H10-72594 proposes a method for improving the capacity for removing metallic impurities by combining citric acid and other organic acids with a complexing solution. However, these cleaning solutions of organic acids are insufficient for removing metallic impurities and incapable of removing particles.
Ammonia water used for removing particles also corrodes copper, hence it is not suitable as cleaning solution after Cu-CMP. Moreover, the use of 2 types of cleaning solution for the cleaning process complicates the production processes and considerably increases the amount of chemicals used. Consequently, a new cleaning technology capable of removing particles and metallic impurities without corroding metallic materials is also needed from the cost point of view and for the protection of the environment.
Thus, when cleaning substrates of electronic materials, a cleaning solution for performing a simple and efficient cleaning without going through a troublesome process is strongly required.
I.e., the object of the present invention is to provide a cleaning solution for substrates of electronic materials capable of removing at the same time metallic impurities and particles from the substrate surface without corroding metallic materials.
In the present invention, the term substrate for electronic materials embraces semiconductor wafers, color filters, substrates of electronic devices for thin-film applications (flat panel devices such as liquid crystals, plasma, EL, etc., optic and magnetic discs, CCD, etc.), etc.